Rice develops first method to sort nanotubes by sizeJune 26, 2006Method sorts nanotubes based on unique electric properties HOUSTON — Rice University scientists have developed the first method for sorting semiconducting carbon nanotubes based on their size, a long-awaited development that could form the basis of a nanotube purification system capable of producing the necessary feedstocks for nano-circuits, therapeutic agents, next-generation power cables and more. Nanotubes, tiny cylinders of carbon no wider than a strand of DNA, possess a tantalizing array of properties coveted by materials scientists. Nanotubes are stronger than steel, but weigh one sixth as much. Some varieties are excellent semiconductors, while others are metals that conduct electricity as well as copper. But there are dozens of varieties of nanotubes, each slightly different in size and atomic structure and each with very different properties. For many applications, engineers need to use just one type of nanotube, but that's not possible today because all production methods turn out a mishmash of types. New research due to appear in an upcoming issue of the Journal of the American Chemical Society describes a new method that uses electric fields to sort nanotubes by size. "People have developed sorting methods based on both chemical and electrical properties, but ours is the first that's capable of sorting semiconducting nanotubes based upon their dielectric constant, which is determined by their diameter," said corresponding author, Howard Schmidt, executive director of Rice's Carbon Nanotechnology Laboratory (CNL). To sort nanotubes, the CNL team built a system that capitalizes on the fact that each type of nanotube has a unique dielectric constant — a term that refers to a material's ability to store electrostatic energy. CNL scientists created an electrified chamber and pumped a solution of dissolved nanotubes through it. The chamber traps metallic nanotubes and causes semiconducting varieties to float at different levels in the chamber. The smaller the diameter of the nanotube, the larger the dielectric constant and the lower in the system the tubes float. By varying the speed of flow through the system — with upper-level currents traveling faster than lower-level currents — the scientists were able to collect samples that had three times more small tubes than large and vice versa. Rice University |
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| Related Nanotubes Current Events and Nanotubes News Articles New study confirms exotic electric properties of graphene First, it was the soccer-ball-shaped molecules dubbed buckyballs. Then it was the cylindrically shaped nanotubes. Now, the hottest new material in physics and nanotechnology is graphene: a remarkably flat molecule made of carbon atoms arranged in hexagonal rings much like molecular chicken wire. Caltech scientists develop DNA origami nanoscale breadboards for carbon nanotube circuits In work that someday may lead to the development of novel types of nanoscale electronic devices, an interdisciplinary team of researchers at the California Institute of Technology (Caltech) has combined DNA's talent for self-assembly with the remarkable electronic properties of carbon nanotubes, thereby suggesting a solution to the long-standing problem of organizing carbon nanotubes into nanoscale electronic circuits. Breakthrough in industrial-scale nanotube processing Rice University scientists today unveiled a method for the industrial-scale processing of pure carbon-nanotube fibers that could lead to revolutionary advances in materials science, power distribution and nanoelectronics. Next-generation microcapsules deliver 'chemicals on demand' Scientists in California are reporting development of a new generation of the microcapsules used in carbon-free copy paper, in which capsules burst and release ink with pressure from a pen. Transforming Nanowires Into Nano-Tools Using Cation Exchange Reactions A team of engineers from the University of Pennsylvania has transformed simple nanowires into reconfigurable materials and circuits, demonstrating a novel, self-assembling method for chemically creating nanoscale structures that are not possible to grow or obtain otherwise. Study shows how carbon nanotubes can affect lining of the lungs Carbon nanotubes are being considered for use in everything from sports equipment to medical applications, but a great deal remains unknown about whether these materials cause respiratory or other health problems. Advance in 'nano-agriculture': Tiny stuff has huge effect on plant growth With potential adverse health and environmental effects often in the news about nanotechnology, scientists in Arkansas are reporting that carbon nanotubes (CNTs) could have beneficial effects in agriculture. A step toward better brain implants using conducting polymer nanotubes Brain implants that can more clearly record signals from surrounding neurons in rats have been created at the University of Michigan. The findings could eventually lead to more effective treatment of neurological disorders such as Parkinson's disease and paralysis. A recipe for controlling carbon nanotubes Nanoscopic tubes made of a lattice of carbon just a single atom deep hold promise for delivering medicines directly to a tumor, sensors so keen they detect the arrival or departure of a single electron, a replacement for costly platinum in fuel cells or as energy‐saving transistors and wires. Friction force differences could offer a new means for sorting and assembling nanotubes Nanotubes and nanowires are promising building blocks for future integrated nanoelectronic and photonic circuits, nanosensors, interconnects and electro-mechanical nanodevices. But some fundamental issues remain to be resolved - among them, how to position and manipulate the tiny tubes. More Nanotubes Current Events and Nanotubes News Articles |
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